Do you not think that the environment of retinoic acid in the water, and hormones in the food, contribute to height? Not to mention if the height development is a dominant trait/phenotype/epigenetic dominant timing mechanism in development (either a longer time of turning on expression or more volume of signal that results in a longer time of expression)? I do.

kolean wrote:Do you not think that the environment of retinoic acid in the water, and hormones in the food, contribute to height? Not to mention if the height development is a dominant trait/phenotype/epigenetic dominant timing mechanism in development (either a longer time of turning on expression or more volume of signal that results in a longer time of expression)? I do.

Much of this falls under the category of diet and health, doesn't it? However, I have not heard that the hormone levels in the food would be the cause of general increase in height: if so, we would see short people among, for example, vegetarians, because vegetables in general do not contain growth hormones or insulin or many of the other growth-promoting hormones of mammalian origin. Also, the average height of humans starts to increase drastically before the feeding of growth-promoting hormones and antibiotics to cattle was started. And what is this thing with retinoic acid? Western people get good amounts of it from their daily diet, how would trace amounts of it in the water affect height?

I am not quite sure what you mean with this litany of dominant trait/phenotype/epigenetic timing mechanism. Height is as far as I know a quantitive trait involving several genes and even if it was caused by a single allele (which it is not), 200 years would not be enough to cause such a dramatic increase in human height, since there has not been heavy evolutionary pressure against short people. There probably is a subtle trend towards increased height to a certain degree because tall people are, according to many studies, somewhat more succesfull in life in general, but this hardly explains the around 10 cm increase in human average height e.g. in Europe and North America during the late 19th century and the 20th century.

Another thing supporting the crucial importance of nutrition and health in human height is the finding that during periods of prosperity (good harvest and favourable climate for years or decades in certain areas) the average height of people was practically as tall as it is today. In medieval Europe, for example, there was a warm period, which was very favourable for people of the time, and alas, according to archaeological findings the people grew very tall during that time.

And to stress my initial point: genes do affect human height (and are the most important single factor), but whether the person reaches the maximum height their genes allow largely depends on his health and diet during childhood and youth. Gender is another similarly affecting trait, actually: both a man and a woman can have the same genes for height, but because of his gender the man will be clearly taller. In the same way, two persons of the same gender can have similar genes for height, but if the other has a very poor diet, he or she is likely to be shorter as an adult.

Finally, what comes to epigenetics: according to some studies epigenetical changes in the gene expression might indeed affect human height, but even this is caused by the diet and health. Generations that undergo, say, famine or encounter severe epidemics, may have shorter children, and even grandchildren. Some scientists say that this could be some kind of "energy saving" mechanism: some of the "tall" genes are downregulated so as to create offspring that require less energy because they are smaller. Lamarck would be happy to hear this :)

Anyway, as far as I know, epigenetics and its role in gene expression in general is still very poorly understood, and its effect on human height is unclear at best.

Okay, basically what Biohazard said (in a nutshell) is that food/technology does not mean evolutionary changes. Why? DNA is not changed, gene expression depending on diet is. Therefore, no evolution. Technology does not mean our DNA changed, no mutations. Therefore, no evolution.

Ok, Biohazard. How do I explain then? We have ceased to go forwards in evolution, mainly 'cos those who have least favorable traits in the environment in which we live in, for instance, one which encourages obesity and health problems, still survive. Those with least favorable traits, therefore still have the chance to produce offspring with their genes. Combine 2 people with least favorable genes and we have offspring with worst genes possible, yet still survive and reproduce. So technically, we are "anti" evolving. Rather than evolving to suit the environment; adapting, our gene pool expands, yet a portion of us have evolved so we are not at all suiting the environment, yet they can still survive and reproduce... am I making sense?

"anti"-evolution is probably a better word. Adapting to struggle more in the environment, rather than less, since humans cheat . All is g?? XD

You are making little sense because you fail to recognize one of the most basic principle of evolution:There is no direction or better direction to evolution.Even if you do not like it the fact that sick, obese, ugly, black, yellow, white and of all shades of skin are reproducing, depending on your set of prejudice is part of the game. The fact that they are fit enough within our societies to reproduce is all that matter. Now even if they could not survive in a different context is completely irrelevant. Taenia would not be able to survive without mammal intestinal tract, yet I would consider them as a species that is highly successfully adapted to its environment.

Patrick

Science has proof without any certainty. Creationists have certainty without
any proof. (Ashley Montague)

I meant that evolution was species adapting better to fit the environment simply 'cos through Natural Selection, only the alleles which benefit the population get passed on. The problem is, that since the environment is no longer an important factor, we are prone to adapt to, for, or no change towards the environment we are in as adapting to fit the environment is no longer important. If so, that means evolution would be altogether pointless in the human species. Anyways, the point is that those with genes which would normally disadvantage someone in an environment without complex rules of society, would still produce offspring, hence the population as a whole is no longer evolving to better fit the environment, but are evolving to least fit the environment. If we were to take species A which evolved from species B because it better survives in the environment, species B would technically be "anti" evolving form of species A, as species A is in turn, less suited to survive in the environment.

Understand? In other words, there is always a "direction" to evolution, as evolution in all species in humans is evolution to better suit the environment- society- to gain mates- to avoid predation etc. However in humans, we no longer evolve to help survival in the environment. In fact, some evolution is considered to be the "opposite" hence, "backwards".

I don't "like" or "dislike" the fact that these people or those people are still reproducing. It's just a fact that they are.

The environment is an important factor. Always. The human made environment is our environment, and is applying selective pressure on human. In what direction, I have no clue, but that does not matter. Evolution is a pointless and directionless thing. It is just the product of random genetic modifications and an ever changing environment. There is no progress or improvement in evolution, just some lucky guys that reproduce faster than some other poor sods and pass its genes more efficiently to the next generation. And evolution is not acting on populations, at least not directly, but on on the individuals within populations.

ANd you are judgmental when you argue that some gene are driving evolution backwards. because you assume that one direction is better than the other. And if someone is leaving more offspring than somebody else he is by definition more fit that the other guy. Even if the fittest is obese, ugly and will die at 40. Live with that.Besides I recall that in the US at least, very rich and powerful men were demonstrated to have larger families than the average population, so maybe the idea that the poor are reproducing like rabbit is just a preconception more than a fact.

Patrick

Science has proof without any certainty. Creationists have certainty without
any proof. (Ashley Montague)

From a genetics point of view, I do not think there can be such a thing as a technical 'anti'-evolution, as I would use the definition to mean the reverse of the evolutionary genome.

Would that not mean that we would have to reverse our genome backwards, and reversing mutations (specific and gross mutations) back the way we came? Which would be next to impossible if we let mother nature do it (in a laboratory setting and with the specific knowledge of evolutionary mutations, then possibly - but how would we get such evolutionary genetic knowledge?).

It also does not make sense in the general concept. We have evolved from an environment that was not hospitable to human life to one that we have manipulated to be hospitable to human life (so much so that the 'fittest' does not have to be the ones that procreate and provide for the 'evolution' of our species). If it was an anti-evolution, then wouldn't we be regressing back to an environment that is not hospitable (which I could see if our way of life is wiped out by a devasting event)?

Human evolution in the future looks as if it will be dominated by genetic manipulation. All the other factors discussed, such as conserving harmful genes by our societal protection of the 'unfit', will pale in comparison to the simple fact that, over the next couple hundred years, humans will manipulate our own genome.

Where is the problem with a genetic illness such as haemophilia, if we consistently remove and replace those genes in the zygote? Will not the would-be parents of the future arrange for their incipient offspring to receive the best gene upgrades for intelligence, good looks, health, athleticism etc?

Forget evolution by natural selection. Instead, think evolution by deliberate gene manipulation. Man of the future will be superman by today's standards.

Humans of the distant future will likely be unrecognisable to those of us today, as humans. They will be too advanced. Designed to be superior.

skeptic wrote:Human evolution in the future looks as if it will be dominated by genetic manipulation. ...

This is indeed possible. However, even if we manipulated our own genes routinely, we would be still subjected to evolution by the means of natural selection: the natural selection would just favour such humans that have a possibility to be gentically modified and when their turn comes, genetically modify others. As long as the replicating entity is the gene or gene complex we are under natural selection - although here the part "natural" might be very far from what it has been before.

In the future, the environment causing the selection pressure would simply be an environment full of gene-manipulating humans and high technology, and whoever spreads their genes best there would prosper in terms of evolutionary success.

There is another thought, if we look beyond the near future. About 10 years ago, I read an article written by a couple of NASA scientists in Scientific American, about the potential for interstellar travel. They suggested that it will take about 1,000 years, but eventually humans will be able to travel between stars at between 10% and 20% of light speed. If we assume they are correct, and humans will develop this way, it allows for interesting speculation.

Project this capability into the distant future (tens of thousands of years), and we can envisage a large part of the human species living either on planets or in space habitats around distant stars. Since travel time between stars is measured in decades, if not centuries, this will create a pretty good genetic barrier. Highly effective reproductive isolation. Each separate population will then be able to evolve, either by natural selection or more probably by artificial genetic manipulation, into a distinct and uniquely different human sub species.

Imagine how many new human descended species might exist in 250,000 years time!

I believe the basis of current evolution is the Law. Those who cannot follow the Law are shut off in prisons and asylums. In prisons and asylums males and females are separated so that they cannot reproduce. Therefore, unless criminals condemned to a life sentence or death sentence are able to escape, their genes will be cut off.

It is naive to think that the whole universe must conform to the sciences devised by the inhabitants of a single planet.